Figure 1

Before an influenza virus can invade a cell, projections (glycoproteins) on the viral and cell outer coverings—membranes—must spread apart to allow the viral membrane (yellow) to approach and merge with the cell membrane (blue). The glycoproteins protrude from the membranes' surface, in somewhat the same way bristles stick out of a hairbrush.

Figure 2

Defensins, the researchers discovered, bind cross-wise to glycoproteins, preventing the viral and cell glycoproteins from spreading apart to allow the viral envelope (yellow) to approach the cell membrane (blue). It's as if the bristles of the hairbrushes were bound together with numerous small rubber bands.

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